JP2010063064A - Picture processor, picture display, method for processing picture and method for displaying picture - Google Patents

Abstract

An image processing device, an image display device, an image processing method, and an image display method that improve the expression of image details without affecting other luminance regions.
An image processing apparatus for correcting an image signal is a luminance component correction amount that calculates a correction amount of a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band. A calculation unit; and a luminance component correction unit that corrects the luminance component of the image signal using the correction amount calculated by the luminance component correction amount calculation unit.
[Selection] Figure 1

Description

  The present invention relates to an image processing device, an image display device, an image processing method, and an image display method.

  In recent years, the number of gradations and dynamic range of video content has increased, and the dark and bright parts of the displayed video cannot be expressed due to insufficient contrast of the display device, and it is often impossible to completely reproduce the details of the dark and bright parts. It has become. In order to express such dark and bright details, an image adaptive tone correction process called monochrome expansion is performed.

  FIG. 19 is an explanatory diagram of the above tone correction processing. In FIG. 19, the horizontal axis represents the horizontal position of the image, and the vertical axis represents the luminance level as the characteristics of the image represented by each image signal during gradation correction processing.

  The input image IMG1 is an image having a low luminance (low gradation) on the left side and a high luminance (high gradation) on the right side, and has a small gradation change even in a low luminance region, and even in a high luminance region. It has a minute gradation change. When the above gradation correction processing is performed on such an input image IMG1, gradation correction is performed according to an upwardly convex gamma correction curve so as to increase overall brightness as shown in FIG. As a result, in the output image IMG2 after gradation correction, the luminance increases on the entire screen, and the luminance is expanded in the low luminance region on the left side, but the average luminance also increases in the low luminance region.

  As described above, in the conventional gradation correction processing, for example, when the dark portion is included in the image, it is possible to express a minute gradation change in the dark portion by increasing the overall luminance so that the luminance on the low gradation side is increased. To. On the other hand, for example, when a bright part is included in an image, the brightness is lowered as a whole so that the brightness on the high gradation side is lowered, so that a minute gradation change in the bright part can be expressed.

  A technique related to such gradation correction processing is disclosed in Patent Document 1, for example. Patent Document 1 discloses a technique for calculating a gamma correction curve corresponding to the average luminance of an input image and correcting the luminance of the input image according to the gamma correction curve. In the technique disclosed in Patent Document 1, the lower the average luminance of the input image, the higher the luminance amplification factor after correction. Further, when the input image is a moving image, flickering of the corrected moving image is suppressed by obtaining a gamma correction curve based on a linear sum of the average luminance of the screen and the average luminance of the previous frame.

JP 2004-266755 A

  However, in the technique disclosed in Patent Document 1, since uniform brightness correction is performed on the entire screen, there is a problem that not only the details of the dark part but also the entire dark part and other brightness areas are expressed brightly. For this reason, when the dark part and the bright part are mixed, for example, details of the dark part can be expressed, but details of the bright part may not be expressed.

  Further, in the technique disclosed in Patent Document 1, since only the luminance component is corrected, the chromaticity of each pixel changes, and the color tendency of the entire screen changes. In this case, there is a possibility that the image quality may be deteriorated only by correcting the luminance component, and it is desirable that the color tendency of the entire screen can be maintained when the details of the image are expressed.

  The present invention has been made in view of the technical problems as described above, and one of its purposes is an image processing apparatus and an image that improve the expression of image details without affecting other luminance regions. A display device, an image processing method, and an image display method are provided.

  In order to solve the above problems, the present invention is an image processing apparatus for correcting an image signal, wherein the luminance component of the image signal is applied only to an image signal in a given luminance level range in a given spatial frequency band. An image processing apparatus comprising: a luminance component correction amount calculation unit that calculates a correction amount; and a luminance component correction unit that corrects the luminance component of the image signal using the correction amount calculated by the luminance component correction amount calculation unit Related to.

  According to the present invention, since the luminance component of the image signal is corrected only for the image signal in the given luminance level range in the given spatial frequency band, uniform correction is performed on the entire screen. Even when the dark part and the bright part are mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed.

  The image processing apparatus according to the present invention may further include a color difference component correction unit that corrects a color difference component of the image signal so that an xy chromaticity value does not change before and after correction by the luminance component correction unit.

  According to the present invention, since the chrominance component is corrected in conjunction with the correction of the luminance component so that the value of the xy chromaticity before and after the correction of the luminance component does not change, in addition to the above effect, It is possible to avoid a situation in which the chromaticity changes and the overall color tendency of the screen changes, and it is possible to maintain the color tendency of the entire screen when expressing image details.

  In the image processing apparatus according to the present invention, the correction amount of the color difference component of the image signal is calculated based on the luminance component of the image signal before and after correction by the luminance component correction unit so that the value of the xy chromaticity does not change. A color difference component correction amount calculation unit that performs correction of the color difference component of the image signal using the color difference component correction amount calculated by the color difference component correction amount calculation unit. .

  According to the present invention, the chrominance component is corrected according to the correction amount of the luminance component in conjunction with the correction of the luminance component of the image signal, so that the value of the xy chromaticity before and after the correction of the luminance component is changed. Therefore, it is possible to correct an image signal that can express details of a dark part and a bright part of an image.

  The image processing apparatus according to the present invention further includes an adjustment parameter storage unit that stores the adjustment parameter of the color difference component, wherein the luminance component before correction is Yin, the luminance component after correction is Yout, and the adjustment parameter is b. Then, the color difference component correction unit corrects the color difference component by multiplying the color difference component of the image signal by the color difference gain with (1-b × (1-Yout / Yin)) as the color difference gain. Can do.

  According to the present invention, the correction of the color difference component linked to the correction of the luminance component of the image signal can be realized by a simple process.

  The image processing apparatus according to the present invention further includes a signal extraction circuit that extracts a signal in the spatial frequency band from the luminance component of the image signal, and the luminance component correction amount calculation unit sets the luminance component level of the image signal to a level. A luminance gain calculation circuit for calculating a corresponding luminance gain, and the luminance component based on the spatial frequency band signal extracted by the signal extraction circuit and the luminance gain calculated by the luminance gain calculation circuit The amount of correction can be calculated.

  According to the present invention, a signal in a given spatial frequency band is extracted by a signal extraction circuit, and a signal in a level range of a given luminance component can be specified by a luminance gain calculation circuit. The luminance component of the image signal can be corrected only for the image signal in the given luminance level range in the given spatial frequency band.

  The image processing apparatus according to the present invention further includes a multistage filter circuit that extracts the spatial frequency band signal from the luminance component of the image signal, and the luminance component correction amount calculation unit is provided for each output of the multistage filter circuit. A plurality of tables for outputting a gain corresponding to the level of the luminance component before correction, and an output of each table constituting the plurality of tables and the output of the multistage filter circuit, provided for each output of the multistage filter circuit And an adder for adding the multiplication results of the multipliers constituting the plurality of multipliers, and calculating an output of the adder as a correction amount of the luminance component. it can.

  According to the present invention, when correcting the luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, a plurality of filters provided for each output of the multistage filter circuit are provided. Since the gain is output from the table, the number of multipliers can be reduced, and low power consumption and low cost can be achieved.

  The image processing apparatus according to the present invention further includes a signal extraction circuit that extracts a signal in the spatial frequency band from the luminance component of the image signal, and the luminance component correction amount calculation unit outputs the output of the signal extraction circuit and the signal before correction. A table for outputting the correction amount of the luminance component corresponding to the level of the luminance component.

  According to the present invention, when correcting a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, the correction amount of the luminance component is output from the table. As a result, the multiplier can be eliminated, and a significant reduction in power consumption and cost can be achieved.

  According to another aspect of the present invention, there is provided an image display device that displays an image based on an image signal, the image processing device according to any one of the above-described methods for correcting the image signal, and the image signal corrected by the image processing device. The present invention relates to an image display device including an image display unit that displays an image.

  According to the present invention, it is possible to provide an image display device that improves the expression of image details without affecting other luminance regions.

  The present invention is also an image display device that displays an image based on an image signal, wherein the spatial frequency changes in a first direction of the image and the image signal in a second direction intersecting the first direction. The image processing unit corrects an image signal of an image in which the level of the luminance component of the image changes and the AC component of the luminance component is uniform throughout, and the image is displayed based on the image signal corrected by the image processing unit An image display unit, and the image display unit relates to an image display device that displays an image in which an alternating current component of luminance is non-uniform in a given luminance level range of a given spatial frequency band.

  According to the present invention, by correcting the luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, the image can be recorded without affecting other luminance regions. It is possible to provide an image display device that improves the expression of details.

  The present invention also relates to an image processing method for correcting an image signal, wherein the luminance for calculating a correction amount of a luminance component of the image signal only for an image signal in a given luminance level range in a given spatial frequency band. The present invention relates to an image processing method including a component correction amount calculation step and a luminance component correction step of correcting the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step.

  According to the present invention, since the luminance component of the image signal is corrected only for the image signal in the given luminance level range in the given spatial frequency band, uniform correction is performed on the entire screen. Even when the dark part and the bright part are mixed, the image signal can be corrected so that the details of both the dark part and the bright part can be expressed.

  The image processing method according to the present invention may further include a color difference component correction step of correcting the color difference component of the image signal so that the value of the xy chromaticity does not change before and after the correction in the luminance component correction step.

  According to the present invention, since the chrominance component is corrected in conjunction with the correction of the luminance component so that the value of the xy chromaticity before and after the correction of the luminance component does not change, in addition to the above effect, It is possible to avoid a situation in which the chromaticity changes and the overall color tendency of the screen changes, and it is possible to maintain the color tendency of the entire screen when expressing image details.

  In the image processing method according to the present invention, the correction amount of the color difference component of the image signal is calculated based on the luminance component of the image signal before and after the correction in the luminance component correction step so that the value of the xy chromaticity does not change. A color difference component correction amount calculating step, wherein the color difference component correction step can correct the color difference component of the image signal using the correction amount of the color difference component calculated in the color difference component correction amount calculation step. .

  According to the present invention, the chrominance component is corrected according to the correction amount of the luminance component in conjunction with the correction of the luminance component of the image signal, so that the value of the xy chromaticity before and after the correction of the luminance component is changed. Therefore, it is possible to correct an image signal that can express details of a dark part and a bright part of an image.

  The image processing method according to the present invention further includes a signal extraction step of extracting a signal in a given spatial frequency band from the luminance component of the image signal, and the luminance component correction amount calculation step includes the luminance component of the image signal. A luminance gain calculation step for calculating a luminance gain corresponding to the level, based on the signal of the spatial frequency band extracted in the signal extraction step and the luminance gain calculated in the luminance gain calculation step, The correction amount of the luminance component can be calculated.

  According to the present invention, a signal in a given spatial frequency band is extracted in the signal extraction step, and a signal in a level range of a given luminance component can be specified in the luminance gain calculation step. The luminance component of the image signal can be corrected only for the image signal in the given luminance level range in the given spatial frequency band.

  The present invention is also an image display method for displaying an image based on an image signal, wherein the correction amount of the luminance component of the image signal is applied only to an image signal in a given luminance level range in a given spatial frequency band. In the luminance component correction step for calculating the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step, and in the luminance component correction step The present invention relates to an image display method including an image display step of displaying an image based on a corrected image signal.

  According to the present invention, it is possible to provide an image display method that improves the expression of image details without affecting other luminance regions.

  The present invention is also an image display method for displaying an image based on an image signal, wherein the spatial frequency changes in a first direction of the image and the image signal in a second direction intersecting the first direction. The image processing step for correcting the image signal of the image in which the level of the luminance component of the image is changed and the AC component of the luminance component is uniform throughout, and the image is displayed based on the image signal corrected in the image processing step An image display step, wherein the image display step relates to an image display method for displaying an image in which an alternating current component of luminance is non-uniform in a given luminance level range of a given spatial frequency band.

  According to the present invention, by correcting the luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band, the image can be recorded without affecting other luminance regions. It is possible to provide an image display method that improves the expression of details.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

  Hereinafter, a projector will be described as an example of the image display device according to the present invention, but the image display device according to the present invention is not limited to the projector.

[Embodiment 1]
FIG. 1 is a block diagram showing a configuration example of an image display system according to the first embodiment of the present invention.

  The image display system 10 includes a projector 20 and a screen SCR. The projector 20 modulates light from a light source (not shown) based on the input image signal, and displays the image by projecting the modulated light onto the screen SCR.

  The projector 20 includes an image processing unit 30 (an image processing device in a broad sense) and a projection unit 100 (an image display unit in a broad sense). The image processing unit 30 corrects the input image signal so that the details of the dark portion and the bright portion of the display image can be expressed without affecting other luminance regions, and outputs the corrected image signal to the projection unit 100. The projection unit 100 projects light modulated based on the image signal from the image processing unit 30 onto the screen SCR.

  FIG. 2 is an explanatory diagram of the gradation correction processing performed in the image processing unit 30 of FIG. In FIG. 2, the horizontal axis represents the horizontal position of the image and the vertical axis represents the luminance level as the characteristics of the image represented by each image signal during gradation correction processing.

The input image IMGin is, for example, an image having a low luminance (low gradation) on the left side and a high luminance (high gradation) on the right side, and has a small gradation change even in a low luminance region, and in a high luminance region. Also have a slight gradation change. Signal extracting means L1 extracts a signal Y _H of the luminance component of the predetermined spatial frequency band from the brightness component of the image signal of the input image IMGin. In Figure 2, the signal extracting unit L1, is set the gain corresponding to the spatial frequency, and extracts a signal Y _H of the luminance components of the gain is large spatial frequency band.

  Further, the luminance gain calculation means G1 calculates a gain coefficient g corresponding to the level of the luminance component of the image signal of the input image. In FIG. 2, the luminance gain calculation unit G1 calculates the gain coefficient g so as to be large in the region where the luminance component level is low, and so that the gain coefficient g becomes substantially zero in the region where the luminance component level is high.

As a result, the multiplier M1 generates a signal gY _H obtained by multiplying the gain coefficient g calculated for the signal Y _H extracted by the signal extracting unit L1 by the brightness gain calculating unit G1. The signal gY _H is a signal corresponding to the correction amount of the luminance component of the input image signal, and the adder A1 adds the luminance component Yin of the input image signal and the signal gY _H to obtain an image signal after gradation correction. Luminance component Yout is output.

  FIG. 3 is a diagram for explaining the operation of the image processing unit 30 in FIG. In FIG. 3, the vertical axis represents the luminance component of the input image signal, and the horizontal axis represents the spatial frequency of the luminance component.

  The image processing unit 30 in FIG. 1 calculates the correction amount of the luminance component of the image signal only in the spatial frequency band Far (a given spatial frequency band), and corrects the luminance component of the image signal using the correction amount. More specifically, the image processing unit 30 has a given level range Yar of the luminance component Yin of the input image signal calculated by the luminance gain calculating unit G1 in the spatial frequency band Far extracted by the signal extracting unit L1. Tone correction is performed on the signal (range Sar in FIG. 3). Thus, given the luminance component Yin of the input image signal, which is the spatial frequency band Far extracted by the signal extraction unit L1 and is calculated by the luminance gain calculation unit G1, without changing the overall luminance tendency. Only in the level range Yar, the luminance component can be changed.

  Since the spatial frequency band extracted by the signal extraction unit L1 and the level range of the luminance component for which the gain coefficient g is calculated by the luminance gain calculation unit G1 can be specified, the specified luminance component of the specified spatial frequency band can be specified. Only in this level range, the luminance change of the input image signal can be amplified. For this reason, for example, in the luminance gain calculation means G1, by increasing the luminance gain coefficient with respect to the low-luminance luminance component that is a dark portion, the details of the dark portion can be expressed without reducing the luminance range of other gradations. Become. In addition, since uniform correction is not performed on the entire screen, even if dark and bright areas are mixed, for example, the brightness of the dark area is uniformly increased, or the brightness of the brightness is also uniformly decreased. It is possible to express both dark and bright details without having to do so.

  Hereinafter, a configuration example of the projector 20 according to the first embodiment that realizes such gradation correction will be described in detail. Hereinafter, an example in which the image signal is composed of the luminance signal Y and the color difference signals U and V will be described, but the image signal according to the present invention is not limited to this.

  FIG. 4 shows a block diagram of a hardware configuration example of the image processing unit 30 in FIG.

  The image processing unit 30 includes a line memory 32, a multistage filter circuit (signal extraction circuit) 40, a luminance signal correction amount calculation circuit (luminance component correction amount calculation unit) 50, and a luminance signal correction circuit (luminance component correction unit) 60. Further, the image processing unit 30 includes a line memory 70, a color difference gain calculation circuit (color difference component correction amount calculation unit) 80, and a color difference signal correction circuit (color difference component correction unit) 90.

  The line memory 32 stores a luminance signal Y (a luminance component of the input image signal) that constitutes the input image signal. The line memory 32 stores the luminance signal Y by the number of lines necessary for the multistage filter circuit 40.

  The multistage filter circuit 40 extracts a signal in a given spatial frequency band from the luminance signal Y (luminance component of the image signal) stored in the line memory 32. This multistage filter circuit 40 can realize the function of the signal extraction means L1 of FIG.

  The luminance signal correction amount calculation circuit 50 calculates the correction amount of the luminance signal based on the output of the multistage filter circuit 40 and the luminance signal stored in the line memory 32. The luminance signal correction amount calculation circuit 50 can calculate a correction amount for a luminance signal in a given luminance level range among luminance signals in a given spatial frequency band extracted by the multistage filter circuit 40. The luminance signal correction amount calculation circuit 50 can realize the function of the luminance gain calculation means G1 shown in FIG.

  The luminance signal correction circuit 60 corrects the luminance signal stored in the line memory 32 using the correction amount calculated by the luminance signal correction amount calculation circuit 50, and outputs the corrected luminance signal Y1.

  The image processing unit 30 can correct the color difference signal in conjunction with the correction of the luminance signal. Therefore, the line memory 70 stores the color difference signals U and V (color difference components of the input image signal) corresponding to the luminance signal in synchronization with the timing at which the luminance signal Y is stored in the line memory 32.

  Based on the luminance signals Y and Y1 before and after correction by the luminance signal correction circuit 60, the color difference gain calculation circuit 80, for example, changes the color difference so that the xy chromaticity value of the XYZ color system (CIE 1931 standard colorimetric system) does not change. The correction amount of the signals U and V is calculated. Here, the color difference gain calculation circuit 80 calculates a gain coefficient corresponding to the correction amount of the color difference signal.

  The color difference signal correction circuit 90 corrects the color difference signals U and V stored in the line memory 70 using the correction amount calculated by the color difference gain calculation circuit 80, and outputs the corrected color difference signals U1 and V1. Thereby, the color difference signal correction circuit 90 can correct the color difference signals U and V so that the value of the xy chromaticity does not change before and after the correction by the luminance signal correction circuit 60.

  As described above, the image processing unit 30 can correct the luminance signal only for the luminance signal having the given luminance level in the given spatial frequency band. Further, the image processing unit 30 can correct the color difference signal according to the correction amount of the luminance signal in conjunction with the correction of the luminance signal.

  Next, each block constituting the image processing unit 30 will be described.

  FIG. 5 shows a block diagram of a configuration example of the multistage filter circuit 40 of FIG. In FIG. 5, the same parts as those in FIG.

  The multistage filter circuit 40 includes first to third filter circuits 42, 44, 46 having different filter sizes. Although FIG. 5 illustrates an example in which the multistage filter circuit 40 performs filter processing with three types of filter circuits, the present invention is not limited to the number of filter circuits.

  The multistage filter circuit 40 includes a plurality of filter circuits having different frequency bands of signals to be extracted, and each filter circuit convolves a pixel value of pixels arranged in the horizontal direction and the vertical direction of an image with a filter coefficient matrix. Output the calculation result.

The first filter circuit 42 can output the filtered result according to the following equation.

  In the above equation, the output of the first filter circuit 42 is FO1, the luminance signal of the coordinates (x, y) is Y (x, y), the filter coefficients are a, (i, j) are relative to the target pixel. Take the range of the above equation in coordinates and let the filter size be s. Each filter circuit receives a luminance signal having the number of lines (the number of vertical scanning lines) corresponding to the filter size.

  Although the above equation shows the output of the first filter circuit 42, the second and third filter circuits 44 and 46 can also output the same filter processing result as the above equation (outputs FO2, FO3). .

  In FIG. 5, the filter size of the first filter circuit 42 is “3”, the filter size of the second filter circuit 44 is “5”, and the filter size of the third filter circuit 46 is “7”. The present invention is not limited to the size.

FIG. 6 shows a block diagram of a configuration example of the luminance signal correction amount calculation circuit 50 of FIG. In FIG. 6, the same parts as those in FIG.
FIG. 7 is an operation explanatory diagram of the weighting calculation circuit 52 of FIG.
FIG. 8 is an operation explanatory diagram of the luminance gain calculation circuit 56 of FIG.

The luminance signal correction amount calculation circuit 50 includes a weighting calculation circuit 52, multipliers 54 _{1 to} 54 ₃ , an adder 55, a luminance gain calculation circuit 56, and a multiplier 58.

The weight calculation circuit 52 receives the outputs of the filter circuits of the first to third filter circuits 42 to 46 constituting the multistage filter circuit 40. Then, as shown in FIG. 7, the weighting calculation circuit 52 calculates weighting coefficients g _{1 to} g ₃ according to combinations of outputs of the filter circuits of the first to third filter circuits 42 to 46.

Such a weight calculation circuit 52 has a lookup table (Look Up Table) in which the input is the output of each filter circuit of the first to third filter circuits 42 to 46 and the output is a weighting coefficient g _{1 to} g _3. , Abbreviated as LUT). Therefore, the weighting calculation circuit 52 includes weighting coefficients (g ₁ a, g ₂ a, g ₃ a), (g) corresponding to combinations of outputs of the first to third filter circuits 42 to 46 in advance. ₁ b, g ₂ b, g ₃ b), (g ₁ c, g ₂ c, g ₃ c),... Are stored, and the filter circuits of the first to third filter circuits 42 to 46 are stored. When the outputs FO1 to FO3 are input, weighting coefficients corresponding to these combinations are output.

Weighting factor _{g 1} is input to the multiplier 54 ₁ outputs FO1 of the first filter circuit 42 is input. The multiplier 54 ₁ outputs the result of multiplying the output FO1 of the first filter circuit 42 by the weighting coefficient g ₁ to the adder 55.

Weighting factor _{g 2,} the output FO2 of the second filter circuit 44 is input to the multiplier 54 ₂ to be inputted. The multiplier 54 ₂ outputs a result of multiplying a weighting factor _{g 2} output FO2 of the second filter circuit 44 to the adder 55.

Weighting factor _{g 3} is input to the multiplier 54 ₃ outputs FO3 of the third filter circuit 46 is input. The multiplier 54 ₃ outputs a result of multiplying a weighting factor _{g 3} output FO3 of the third filter circuit 46 to the adder 55.

The adder 55 adds the multiplication results of the multipliers 54 _{1 to} 54 ₃ and outputs the addition result to the multiplier 58. The multiplier 58 receives the luminance gain coefficient h calculated by the luminance gain calculation circuit 56.

  A luminance signal constituting the input image signal is input to the luminance gain calculation circuit 56. Then, as shown in FIG. 8, the luminance gain calculation circuit 56 calculates a luminance gain coefficient h (luminance gain) corresponding to the level of the luminance signal (the level of the luminance component of the image signal).

  Such a luminance gain calculation circuit 56 is realized by an LUT having an input as a luminance signal (luminance component of an image signal) and an output as a luminance gain coefficient h. Therefore, the luminance gain calculation circuit 56 stores in advance luminance gain coefficients ha, hb, hc,... Corresponding to the luminance signals (input luminance signals) constituting the input image signal, and constitutes the input image signal. When a luminance signal to be input is input, a luminance gain coefficient corresponding to the luminance signal is output. In this luminance gain calculation circuit 56, a luminance gain coefficient corresponding to a desired luminance signal can be designated, so that a correction amount can be generated only for the designated gradation.

  The multiplier 58 multiplies the addition result of the adder 55 by the luminance gain coefficient h from the luminance gain calculation circuit 56 to output a correction signal VA corresponding to the correction amount of the luminance signal. The correction signal VA is input to the luminance signal correction circuit 60.

  As described above, the luminance signal correction amount calculation circuit 50 includes the signal of the given spatial frequency band extracted by the multistage filter circuit 40 (signal extraction circuit in a broad sense) and the luminance gain calculated by the luminance gain calculation circuit 56. The correction amount of the luminance signal can be calculated based on the coefficient. Then, the luminance signal correction circuit 60 outputs the corrected luminance signal Y1 by adding the correction signal VA from the luminance signal correction amount calculation circuit 50 to, for example, the luminance signal constituting the input image signal.

  In addition, the correction process of the color difference signal according to the correction amount of the luminance signal in conjunction with the correction of the luminance signal can be realized by the following configuration.

  FIG. 9 shows a block diagram of a configuration example of the color difference gain calculation circuit 80 of FIG. 9, the same parts as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  The color difference gain calculation circuit 80 includes a color difference signal adjustment circuit 82 and an adjustment parameter storage unit 84. The color difference signal adjustment circuit 82 stores the luminance signal (the luminance component of the input image signal) Yin constituting the input image signal, the luminance signal Yout corrected as described above, and the adjustment parameter storage unit 84. The adjustment parameter b is input. Then, the color difference signal adjustment circuit 82 calculates a color difference gain coefficient (color difference gain) gc using the luminance signals Yin and Yout and the adjustment parameter b.

More specifically, the color difference gain calculation circuit 80 calculates the color difference gain coefficient gc according to the following equation.

  In the above equation, the adjustment parameter b is a parameter for adjusting the chromaticity. When the adjustment parameter b is “0”, the color difference signal (color difference component) constituting the input image signal is output as it is without being corrected. On the other hand, when the adjustment parameter b is “1”, the chrominance signal is also corrected according to the correction amount of the luminance signal so that the chromaticity does not change before and after the correction of the luminance signal of the input image signal. The adjustment parameter b can be a value larger than “0” and smaller than “1”, but in the first embodiment, the adjustment parameter b is preferably “1”.

  FIG. 10 is an explanatory diagram of an operation example of the color difference gain calculation circuit 80 of FIG. In FIG. 10, it is assumed that the adjustment parameter b is “1”.

  When the color space indicating the luminance signal on the vertical axis and the color difference signal on the horizontal axis is represented, the RGB R component, G component, and B component are defined in the directions shown in FIG. Here, the area DISP represents a color gamut that can be reproduced by a display device. At this time, when the color of the input image signal is the coordinate P0, the values in the xy chromaticity diagram are equal on the isoline SV passing through the coordinate P0.

  However, if the luminance signal constituting the input image signal is corrected as described above, it moves to the coordinate P1. For this reason, the coordinate P1 does not exist on the isoline SV, and the color tendency after the luminance signal is corrected changes.

  Therefore, in the color difference gain calculation circuit 80, the color difference gain coefficient gc is used to correct the color difference signal in accordance with the correction amount of the luminance signal so as to convert the color of the input signal at the coordinate P0 into the coordinate P2 on the isoline SV. Is calculated. As a result, even if the luminance signal is corrected, the color tendency of the entire screen can be maintained without changing the corrected luminance level. Therefore, natural correction can be realized without changing the chromaticity of each pixel before and after correction.

  The color difference gain coefficient gc calculated in this way is input to the color difference signal correction circuit 90. The color difference signal correction circuit 90 multiplies the color difference signal U from the line memory 70 by the color difference gain coefficient gc, and multiplies the color difference signal V from the line memory 70 by the color difference gain coefficient gc. The color difference signals U and V corrected in this way are input to the projection unit 100.

  As described above, the image processing unit 30 can correct not only the luminance signal but also the color difference signal in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained.

  The processing of the image processing unit 30 in the first embodiment can also be realized by software processing. In this case, the image processing unit 30 includes a central processing unit (hereinafter abbreviated as “CPU”), a read only memory (hereinafter abbreviated as “ROM”), or a random access memory (hereinafter “Random Access Memory”). The CPU that reads a program stored in the ROM or RAM controls the hardware such as a multiplier and an adder by executing processing corresponding to the program, and the above luminance Component and color difference component correction processing is performed.

  FIG. 11 is a flowchart of an example of luminance signal correction processing performed by the image processing unit 30 according to the first embodiment. When the processing in FIG. 11 is realized by software, a program for realizing the processing shown in FIG. 11 is stored in a ROM or RAM built in the image processing unit 30.

  First, as the input luminance signal accumulation step, the image processing unit 30 accumulates a luminance signal (input luminance signal) constituting the input image signal (step S10). In this case, the luminance signal is stored in the line memory 32 or a RAM that realizes the function of the line memory 32.

  Next, the image processing unit 30 extracts a specific spatial frequency band of the luminance signal as a signal extraction step (step S12). For example, a luminance signal in a given spatial frequency band is extracted by the multistage filter circuit 40. Alternatively, in the case of realizing by software processing, the CPU extracts a luminance signal in the above spatial frequency band by controlling a multiplier or an adder that realizes the function of the multistage filter circuit 40.

  Subsequently, the image processing unit 30 calculates the correction amount of the luminance signal as the luminance component correction amount calculation step (step S14). In other words, the luminance signal correction amount calculation circuit 50 is weighted according to the signal extracted by the multistage filter circuit 40, and then multiplied by a coefficient corresponding to the luminance level of the luminance signal constituting the input image signal. Is output. Alternatively, when implemented by software processing, the CPU weights the signal according to the signal extracted by the signal extraction processing, and then multiplies the correction signal VA by the coefficient corresponding to the luminance level of the luminance signal constituting the input image signal. Generate. That is, in step S14, as a luminance gain calculation step, a luminance gain corresponding to the level of the luminance component of the image signal is calculated. Then, the correction amount of the luminance component is calculated based on the spatial frequency band signal extracted in step S12 and the luminance gain calculated in step S14.

  Then, as the luminance component correction step, the image processing unit 30 corrects the luminance signal constituting the input image signal using the correction amount calculated in step S14 (step S16), and outputs the corrected luminance signal. (Step S18), and a series of processing ends (end). That is, in step S16, the luminance signal correction circuit 60 adds the correction signal VA to the luminance signal constituting the input image signal to generate a corrected luminance signal. Alternatively, when realized by software processing, the CPU adds the correction signal VA to the luminance signal constituting the input image signal to generate a corrected luminance signal.

  FIG. 12 is a flowchart of an example of the color difference signal correction process performed by the image processing unit 30 according to the first embodiment. When the processing in FIG. 12 is realized by software, a program for realizing the processing shown in FIG. 12 is stored in a ROM or RAM built in the image processing unit 30.

  First, the image processing unit 30 accumulates color difference signals (input color difference signals) constituting the input image signal as an input color difference signal accumulation step (step S20). In this case, the color difference signal is stored in the line memory 32 or a RAM that realizes the function of the line memory 32.

  Next, as the color difference component correction amount calculation step, the image processing unit 30 calculates a color difference gain coefficient for adjusting the color difference signal according to the luminance signal before and after correction in the luminance signal correction processing of FIG. 11 (step S22). . For example, the color difference signal adjustment circuit 82 outputs the color difference gain coefficient gc corresponding to the luminance signal before and after the correction and the adjustment parameter designated in advance. Alternatively, when realized by software processing, the CPU outputs the color difference gain coefficient gc according to the above equation (2) using the predetermined adjustment parameter b. As described above, in step S22, the correction amount of the color difference component of the image signal is calculated so that the value of the xy chromaticity does not change before and after the correction in the luminance component correction step.

  Subsequently, as the color difference component correction step, the image processing unit 30 corrects the color difference signal constituting the input image signal using the color difference component correction amount (color difference gain coefficient) calculated in step S22 (step S24). Then, the corrected color difference signal is output (step S26), and a series of processing ends (end). That is, in step S24, the color difference signal correction circuit 90 multiplies the color difference signal constituting the input image signal by the color difference gain coefficient calculated in step S22 to generate a corrected color difference signal. Alternatively, when realized by software processing, the CPU generates a corrected color difference signal by multiplying the color difference signal constituting the input image signal by the color difference gain coefficient. Thus, in step S24, the color difference component of the image signal is corrected so that the xy chromaticity value does not change before and after the correction in the luminance component correction step.

  The luminance signal Y1 and the color difference signals U1 and V1 corrected by the image processing unit 30 are output to the projection unit 100. The projection unit 100 can modulate light from the light source based on the luminance signal Y1 and the color difference signals U1 and V1, and project the modulated light onto the screen SCR.

  FIG. 13 shows a diagram of a configuration example of the projection unit 100 of FIG. In FIG. 13, the projection unit 100 according to the first embodiment is described as being configured by a so-called three-plate liquid crystal projector, but the projection unit of the image display device according to the present invention is configured by a so-called three-plate liquid crystal projector. It is not limited to things. That is, in the following description, it is assumed that one pixel is composed of an R component sub-pixel, a G component sub-pixel, and a B component sub-pixel, but the number of sub-pixels (color component number) constituting one pixel is It is not limited.

  In FIG. 13, the luminance signal Y1 and the color difference signals U1 and V1 input from the image processing unit 30 are converted into image signals of RGB color components, and then light from the light source is modulated for each color component. And In this case, the RGB signal conversion circuit may be included in the image processing unit 30 or the projection unit 100.

  The projection unit 100 according to the first embodiment includes a light source 110, integrator lenses 112 and 114, a polarization conversion element 116, a superimposing lens 118, an R dichroic mirror 120R, a G dichroic mirror 120G, a reflection mirror 122, and an R field lens 124R and G. Field lens 124G, R liquid crystal panel 130R (first light modulation element), G liquid crystal panel 130G (second light modulation element), B liquid crystal panel 130B (third light modulation element), relay optical system 140, a cross dichroic prism 160, and a projection lens 170. The liquid crystal panels used as the R liquid crystal panel 130R, the G liquid crystal panel 130G, and the B liquid crystal panel 130B are transmissive liquid crystal display devices. The relay optical system 140 includes relay lenses 142, 144, and 146 and reflection mirrors 148 and 150.

  The light source 110 is composed of, for example, an ultra-high pressure mercury lamp, and emits light including at least R component light, G component light, and B component light. The integrator lens 112 has a plurality of small lenses for dividing the light from the light source 110 into a plurality of partial lights. The integrator lens 114 has a plurality of small lenses corresponding to the plurality of small lenses of the integrator lens 112. The superimposing lens 118 superimposes the partial light emitted from the plurality of small lenses of the integrator lens 112 on the liquid crystal panel.

  The polarization conversion element 116 includes a polarization beam splitter array and a λ / 2 plate, and converts light from the light source 110 into substantially one type of polarized light. The polarization beam splitter array has a structure in which a polarization separation film that separates partial light divided by the integrator lens 112 into p-polarization and s-polarization, and a reflection film that changes the direction of light from the polarization separation film are alternately arranged. Have. The polarization direction of the two types of polarized light separated by the polarization separation film is aligned by the λ / 2 plate. Light that has been converted into substantially one type of polarized light by the polarization conversion element 116 is applied to the superimposing lens 118.

  The light from the superimposing lens 118 enters the R dichroic mirror 120R. The R dichroic mirror 120R has a function of reflecting R component light and transmitting G component and B component light. The light transmitted through the R dichroic mirror 120R is applied to the G dichroic mirror 120G, and the light reflected by the R dichroic mirror 120R is reflected by the reflection mirror 122 and guided to the R field lens 124R.

  The dichroic mirror for G 120G has a function of reflecting G component light and transmitting B component light. The light transmitted through the G dichroic mirror 120G enters the relay optical system 140, and the light reflected by the G dichroic mirror 120G is guided to the G field lens 124G.

  In the relay optical system 140, in order to minimize the difference between the optical path length of the B component light transmitted through the G dichroic mirror 120G and the optical path length of the other R component and G component light, the relay lenses 142, 144, 146 is used to correct the difference in optical path length. The light transmitted through the relay lens 142 is guided to the relay lens 144 by the reflection mirror 148. The light transmitted through the relay lens 144 is guided to the relay lens 146 by the reflection mirror 150. The light transmitted through the relay lens 146 is applied to the B liquid crystal panel 130B.

  The light applied to the R field lens 124R is converted into parallel light and is incident on the R liquid crystal panel 130R. The R liquid crystal panel 130R functions as a light modulation element (light modulation unit), and the transmittance (passage rate, modulation rate) changes based on the R image signal. Therefore, the light (first color component light) incident on the R liquid crystal panel 130R is modulated based on the R image signal, and the modulated light is incident on the cross dichroic prism 160.

  The light applied to the G field lens 124G is converted into parallel light and is incident on the G liquid crystal panel 130G. The G liquid crystal panel 130G functions as a light modulation element (light modulation unit), and the transmittance (passage rate, modulation rate) changes based on the G image signal. Therefore, the light (second color component light) incident on the G liquid crystal panel 130G is modulated based on the G image signal, and the modulated light is incident on the cross dichroic prism 160.

  The B liquid crystal panel 130B irradiated with the light converted into parallel light by the relay lenses 142, 144, and 146 functions as a light modulation element (light modulation unit), and has a transmittance (passage rate) based on the B image signal. , Modulation rate) is changed. Therefore, the light (third color component light) incident on the B liquid crystal panel 130B is modulated based on the B image signal, and the modulated light is incident on the cross dichroic prism 160.

  The R liquid crystal panel 130R, the G liquid crystal panel 130G, and the B liquid crystal panel 130B have the same configuration. Each liquid crystal panel is a liquid crystal, which is an electro-optical material, sealed in a pair of transparent glass substrates. For example, a polysilicon thin film transistor is used as a switching element, and the transmittance of each color light corresponding to the image signal of each sub-pixel. Modulate.

  In the first embodiment, a liquid crystal panel serving as a light modulation element is provided for each color component constituting one pixel, and the transmittance of each liquid crystal panel is controlled by an image signal corresponding to a sub pixel. That is, the image signal for the R component sub-pixel is used to control the transmittance (transmission rate, modulation factor) of the R liquid crystal panel 130R, and the image signal for the G component sub pixel is used for the G liquid crystal panel 130G. The B component sub-pixel image signal is used to control the transmittance of the B liquid crystal panel 130B. In the first embodiment, contrast processing is performed on the image signal for each color component, and the image signal after the contrast processing is converted into a signal corresponding to the pixel value of each RGB color component and provided for each color component. The transmittance of each liquid crystal panel is controlled.

  The cross dichroic prism 160 has a function of outputting combined light obtained by combining incident light from the R liquid crystal panel 130R, the G liquid crystal panel 130G, and the B liquid crystal panel 130B as outgoing light. The projection lens 170 is a lens that enlarges and forms an output image on the screen SCR.

  After performing the gradation correction process in the first embodiment, by controlling the projection unit 100 as an image display step and displaying an image based on the image signal corrected in the gradation correction process, It is possible to provide an image display method that improves the expression of image details without affecting other luminance regions.

  As described above, according to the first embodiment, not only the luminance signal but also the color difference signal is corrected in conjunction with the luminance signal. At this time, for the luminance signal, only a given luminance level range is corrected in a given spatial frequency band. Therefore, a test in which the spatial frequency changes in the first direction of the image, the level of the luminance component of the image signal changes in the second direction intersecting the first direction, and the AC component of the luminance component is uniform throughout. When an image is input, the projector 20 displays the following image.

  FIG. 14 schematically shows a test image in the first embodiment.

  In this test image, the spatial frequency gradually changes in the vertical direction (first direction) of the image (for example, changes from a high frequency to a low frequency in the first direction) and the horizontal direction of the image (crosses the first direction). In the second direction, the level of the luminance component of the image signal gradually changes (for example, changes from low luminance to high luminance in the second direction), and the AC component of the luminance component is uniform throughout. When such a test image is input to the projector 20, the image processing unit 30 corrects the luminance signal only in a given luminance level range in a given spatial frequency band. For this reason, the projector 20 to which the test image shown in FIG. 14 is input displays an image in which the alternating current component of luminance is non-uniform in a given luminance level range in a given spatial frequency band.

  That is, when the image signal of the test image is corrected by the gradation correction process in the first embodiment as the image processing step, and then the image is displayed based on the image signal after the gradation correction process as the image display step. , Display an image in which the alternating current component of luminance is non-uniform in a given luminance level range of a given spatial frequency band.

  Therefore, by setting the extracted spatial frequency band to a desired band and setting the luminance level range to a desired range, it is possible to provide the projector 20 capable of expressing the details of the dark part and the bright part of the image.

  In FIG. 14, the first direction is the vertical direction of the image, and the second direction is the horizontal direction of the image. However, the first direction is the horizontal direction of the image, and the second direction is the vertical direction of the image. The same applies to the direction.

[Embodiment 2]
In the image processing unit 30 according to the first embodiment, the luminance signal correction amount calculation circuit 50 includes a weighting calculation circuit 52 and a luminance gain calculation circuit 56 as illustrated in FIG. 6, and multiplies the weighting coefficient and the luminance gain coefficient. The correction signal VA is generated by the multiplier, but the present invention is not limited to this.

  FIG. 15 is a block diagram showing a configuration example of the luminance signal correction amount calculation circuit 200 according to the second embodiment of the present invention. For example, instead of the luminance signal correction amount calculation circuit 50 in the first embodiment, the luminance signal correction amount calculation circuit 200 shown in FIG. 15 is built in the image processing unit 30 of FIG.

The luminance signal correction amount calculation circuit 200 includes first to third LUTs 202 _{1 to} 202 ₃ , multipliers 204 _{1 to} 204 ₃ , and an adder 206. The luminance signal correction amount calculation circuit 200 multiplies each output of the multistage filter circuit 40 by the luminance gain coefficient from each of the _{first to third} LUTs 202 _{1 to} 202 ₃ , and then adds each multiplication result. Output as a correction signal VA.

FIG. 16A, FIG. 16B, and FIG. 16C show operation explanatory diagrams of the _first to third LUTs 202 _{1 to} 202 ₃ in FIG.

The first LUT 202 ₁ receives a luminance signal constituting the input image signal and outputs a luminance gain coefficient j ₁ corresponding to the luminance signal. Therefore, the first LUT 202 ₁ stores in advance luminance gain coefficients j ₁ a, j ₁ b, j ₁ c... Corresponding to the luminance signal, and when the luminance signal is input, the luminance signal is stored in the luminance signal. corresponding luminance gain coefficient is output as the brightness gain coefficient j _1.

The second LUT 202 _2, the luminance signal which forms the input image signal and outputs a brightness gain coefficient j ₂ corresponding to the brightness signal. Therefore, the second LUT 202 ₂ stores in advance the luminance gain coefficients j ₂ a, j ₂ b, j ₂ c... Corresponding to the luminance signal, and when the luminance signal is inputted, corresponding luminance gain coefficient is output as the brightness gain coefficient j _2.

The third LUT 202 ₃ receives a luminance signal constituting the input image signal and outputs a luminance gain coefficient j ₃ corresponding to the luminance signal. Therefore, the third LUT 202 ₃ stores in advance luminance gain coefficients j ₃ a, j ₃ b, j ₃ c... Corresponding to the luminance signal, and when the luminance signal is input, the luminance signal is added to the luminance signal. corresponding luminance gain coefficient is output as the brightness gain coefficient j _3.

15, the multiplier 204 ₁ multiplies the brightness gain coefficient _{j 1} from the output FO1 the first LUT 202 ₁ of the first filter circuit 42 constituting the multi-stage filter circuit 40, adds the multiplication results 206 Output to. The multiplier 204 ₂ multiplies the brightness gain coefficient _{j 2} from the output FO2 and the second LUT 202 ₂ of the second filter circuit 44 constituting the multi-stage filter circuit 40, and outputs the multiplication result to the adder 206. The multiplier 204 ₃ multiplies the brightness gain coefficient _{j 3} from the output FO3 the third LUT 202 ₃ of the third filter circuit 46 constituting the multi-stage filter circuit 40, and outputs the multiplication result to the adder 206.

The adder 206 adds the multiplication results of the multipliers 204 _{1 to} 204 ₃ and outputs the addition result as a correction signal VA.

  As described above, the image processing unit according to the second embodiment includes the multistage filter circuit 40 that extracts a signal in a given spatial frequency band from the luminance component of the image signal, and the luminance signal correction amount calculation circuit 200 includes the multistage filter circuit. A plurality of tables that are provided for each of the 40 outputs and output gain corresponding to the level of the luminance component before correction, and outputs of the multistage filter circuit 40 that are provided for each output of the multistage filter circuit 40 and the above-described plurality of tables are configured. A plurality of multipliers for multiplying the outputs of the tables to be added, and an adder for adding the multiplication results of the plurality of multipliers, and the output of the adder can be calculated as a correction amount of the luminance component.

  According to the second embodiment, as in the first embodiment, not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained. In addition, when the test image shown in FIG. 14 is input, as in the first embodiment, an image in which the AC component of luminance is non-uniform in a given luminance level range in a given spatial frequency band is displayed. .

  Further, according to the second embodiment, compared with the first embodiment, the number of multipliers built in the luminance signal correction amount calculation circuit can be reduced, so that it is possible to reduce power consumption and cost. .

[Embodiment 3]
As shown in FIG. 15, the luminance signal correction amount calculation circuit 200 according to the second embodiment includes _first to third LUTs 202 _{1 to} 202 ₃ , multipliers 204 _{1 to} 204 _3, and an adder 206. Although the multiplication results of the multipliers using the luminance gain coefficients from the _first to third LUTs 202 _{1 to} 202 ₃ are added, the present invention is not limited to this.

  FIG. 17 shows a block diagram of a configuration example of the luminance signal correction amount calculation circuit 250 according to the third embodiment of the present invention. For example, instead of the luminance signal correction amount calculation circuit 50 in the first embodiment, a luminance signal correction amount calculation circuit 250 shown in FIG. 17 is built in the image processing unit 30 of FIG.

  The luminance signal correction amount calculation circuit 250 includes an LUT 252. The luminance signal correction amount calculation circuit 250 outputs the output from the LUT 252 as the correction signal VA.

  FIG. 18 is a diagram for explaining the operation of the LUT 252 in FIG.

  The LUT 252 receives the luminance signal constituting the input image signal and the outputs FO1 to FO3 of the filter circuits of the first to third filter circuits 42 to 44 constituting the multistage filter circuit 40, and the luminance signal and each filter A correction amount corresponding to the combination with the output of the circuit is output. This correction amount is output as a correction signal VA. For this reason, the LUT 252 stores correction amounts VAa, VAb,..., VAc, VAd, VAe,... Corresponding to combinations of the luminance signal and the outputs FO1 to FO3 of the respective filter circuits in advance. When a signal and the output of each filter circuit are input, a correction amount corresponding to the combination of these is output.

  As described above, the image processing unit according to the third embodiment includes the multistage filter circuit (signal extraction circuit in a broad sense) 40 that extracts a signal in a given spatial frequency band from the luminance component of the image signal, and the luminance signal correction amount. The calculation circuit 250 can include a table for outputting the correction amount of the luminance component corresponding to the output of the multistage filter circuit 40 and the level of the luminance component before correction. Then, the correction amount output by this table is output as the correction signal VA.

  According to the third embodiment, similarly to the first or second embodiment, not only the luminance signal but also the color difference signal can be corrected in conjunction with the luminance signal. This avoids a situation in which the chromaticity of each pixel changes according to the correction amount of the luminance signal and the overall color tendency of the screen changes, and when the details of the image are expressed, The tendency can be maintained. When the test image shown in FIG. 14 is input, an image in which the AC component of luminance is non-uniform in a given luminance level range in a given spatial frequency band is displayed as in the first or second embodiment. Will do.

  Further, according to the third embodiment, compared with the first or second embodiment, the multiplier and the adder built in the luminance signal correction amount calculation circuit can be eliminated, so that the power consumption can be greatly reduced. Cost reduction is possible.

  The image processing apparatus, the image display apparatus, the image processing method, and the image display method according to the present invention have been described based on the above embodiment, but the present invention is not limited to the above embodiment, and the gist thereof The present invention can be implemented in various forms without departing from the scope of the invention, and for example, the following modifications are possible.

  (1) In each of the above embodiments, the projector has been described as an example of the image display device, but the present invention is not limited to this. The image display device according to the present invention can be applied to all devices that perform image display, such as liquid crystal display devices, plasma display devices, and organic EL display devices.

  (2) In each of the above embodiments, the light valve using a transmissive liquid crystal panel is used as the light modulation element. However, the present invention is not limited to this. For example, DLP (Digital Light Processing) (registered trademark), LCOS (Liquid Crystal On Silicon), or the like may be employed as the light modulation element.

  (3) In each of the above embodiments, a light valve using a so-called three-plate transmission type liquid crystal panel as a light modulation element has been described as an example. A light valve using a liquid crystal panel of a type may be adopted.

  (4) In each of the above-described embodiments, one pixel is described as being composed of three color component sub-pixels, but the present invention is not limited to this. The number of color components constituting one pixel may be 2, or 4 or more.

  (5) In each of the above embodiments, the present invention has been described as an image processing apparatus, an image display apparatus, an image processing method, and an image display method, but the present invention is not limited to this. For example, an image display system including the image processing apparatus and the image display apparatus described above may be used. Alternatively, for example, a program describing a processing procedure of an image processing apparatus processing method (image processing method) for realizing the present invention or an image display apparatus processing method (image display method) for realizing the present invention. Or a recording medium on which the program is recorded.

1 is a block diagram of a configuration example of an image display system in Embodiment 1 according to the present invention. FIG. 3 is an explanatory diagram of gradation correction processing performed in the image processing unit of FIG. 1. FIG. 3 is an operation explanatory diagram of the image processing unit in FIG. 1. The block diagram of the hardware structural example of the image process part of FIG. The block diagram of the structural example of the multistage filter circuit of FIG. FIG. 5 is a block diagram of a configuration example of a luminance signal correction amount calculation circuit in FIG. 4. FIG. 7 is an operation explanatory diagram of the weight calculation circuit of FIG. 6. FIG. 7 is an operation explanatory diagram of the luminance gain calculation circuit of FIG. 6. FIG. 5 is a block diagram of a configuration example of a color difference gain calculation circuit in FIG. 4. Explanatory drawing of the operation example of the color difference gain calculation circuit of FIG. FIG. 3 is a flowchart of a luminance signal correction process example of the image processing unit according to the first embodiment. FIG. 3 is a flowchart of a color difference signal correction process example of the image processing unit according to the first embodiment. The figure of the structural example of the projection part of FIG. FIG. 3 is a diagram schematically illustrating a test image in the first embodiment. The block diagram of the structural example of the luminance signal correction amount calculation circuit in Embodiment 2 which concerns on this invention. FIGS. 16A, 16B, and 16C are explanatory diagrams of operations of the first to third LUTs of FIG. The block diagram of the structural example of the luminance signal correction amount calculation circuit in Embodiment 3 which concerns on this invention. FIG. 18 is an operation explanatory diagram of the LUT in FIG. 17. Explanatory drawing of the conventional gradation correction process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image display system, 20 ... Projector, 30 ... Image processing part,
32, 70 ... line memory, 40 ... multistage filter circuit, 42 ... first filter circuit,
44 ... 2nd filter circuit, 46 ... 3rd filter circuit,
50, 200, 250 ... luminance signal correction amount calculation circuit, 52 ... weighting calculation circuit,
54 _{1 to} 54 ₃ , 58, 204 _{1 to} 204 ₃ , M1.
55, 206, A1 ... adder, 56 ... luminance gain calculation circuit,
60 ... Luminance signal correction circuit, 80 ... Color difference gain calculation circuit, 82 ... Color difference signal adjustment circuit,
84 ... Adjustment parameter storage unit, 90 ... Color difference signal correction circuit, 100 ... Projection unit,
110 ... light source, 112,114 ... integrator lens,
116: Polarization conversion element, 118 ... Superposition lens,
120R ... Dichroic mirror for R, 120G ... Dichroic mirror for G,
122, 148, 150 ... reflective mirror, 124R ... field lens for R,
124G ... G field lens, 130R ... R liquid crystal panel,
130G ... G liquid crystal panel, 130B ... B liquid crystal panel,
140: relay optical system, 142, 144, 146 ... relay lens,
160: Cross dichroic prism, 170 ... Projection lens,
202 ₁ ... 1st LUT, 202 ₂ ... 2nd LUT, 202 ₃ ... 3rd LUT,
252 ... LUT, FO1 to FO3 ... output of the filter circuit,
G1 ... Luminance gain calculation means, L1 ... Signal extraction means, SCR ... Screen,
Y, Y1 ... Luminance signal, U, U1, V, V1 ... Color difference signal

Claims (15)

An image processing apparatus for correcting an image signal,
A luminance component correction amount calculation unit that calculates a correction amount of a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band;
An image processing apparatus comprising: a luminance component correction unit that corrects a luminance component of the image signal using the correction amount calculated by the luminance component correction amount calculation unit. In claim 1,
An image processing apparatus comprising: a color difference component correction unit that corrects a color difference component of the image signal so that an xy chromaticity value does not change before and after correction by the luminance component correction unit. In claim 2,
A color difference component correction amount calculation unit that calculates a correction amount of the color difference component of the image signal based on the luminance component of the image signal before and after correction by the luminance component correction unit so that the value of xy chromaticity does not change;
The color difference component correction unit is
An image processing apparatus that corrects a color difference component of the image signal using a correction amount of the color difference component calculated by the color difference component correction amount calculation unit. In claim 3,
An adjustment parameter storage unit that stores adjustment parameters of the color difference component;
When the luminance component before correction is Yin, the luminance component after correction is Yout, and the adjustment parameter is b,
The color difference component correction unit
An image processing apparatus, wherein (1-b × (1-Yout / Yin)) is used as a color difference gain, and the color difference component is corrected by multiplying the color difference component of the image signal by the color difference gain. In any one of Claims 1 thru | or 4,
A signal extraction circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
A luminance gain calculation circuit for calculating a luminance gain corresponding to the level of the luminance component of the image signal;
An image processing apparatus that calculates a correction amount of the luminance component based on the signal in the spatial frequency band extracted by the signal extraction circuit and the luminance gain calculated by the luminance gain calculation circuit. . In any one of Claims 1 thru | or 4,
A multi-stage filter circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
A plurality of tables that are provided for each output of the multi-stage filter circuit and output a gain corresponding to the level of the luminance component before correction;
A plurality of multipliers that are provided for each output of the multi-stage filter circuit, and multiply the outputs of the multi-stage filter circuit and the outputs of the tables constituting the plurality of tables;
An adder for adding the multiplication results of each multiplier constituting the plurality of multipliers,
An image processing apparatus that calculates an output of the adder as a correction amount of the luminance component. In any one of Claims 1 thru | or 4,
A signal extraction circuit for extracting a signal of the spatial frequency band from a luminance component of the image signal;
The luminance component correction amount calculation unit
An image processing apparatus comprising: a table for outputting a correction amount of the luminance component corresponding to the output of the signal extraction circuit and the level of the luminance component before correction. An image display device that displays an image based on an image signal,
The image processing apparatus according to claim 1, wherein the image signal is corrected;
An image display device comprising: an image display unit that displays an image based on the image signal corrected by the image processing device. An image display device that displays an image based on an image signal,
The spatial frequency changes in the first direction of the image, the level of the luminance component of the image signal changes in the second direction that intersects the first direction, and the AC component of the luminance component is uniform throughout. An image processor for correcting the image signal of the image;
An image display unit that displays an image based on the image signal corrected by the image processing unit,
The image display unit is
An image display device that displays an image in which an alternating current component of luminance is non-uniform in a given luminance level range in a given spatial frequency band. An image processing method for correcting an image signal,
A luminance component correction amount calculating step for calculating a correction amount of a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band;
And a luminance component correction step of correcting the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step. In claim 10,
An image processing method comprising: a color difference component correction step of correcting a color difference component of the image signal so that an xy chromaticity value does not change before and after the correction in the luminance component correction step. In claim 11,
A color difference component correction amount calculating step for calculating a correction amount of the color difference component of the image signal so that the value of the xy chromaticity does not change based on the luminance component of the image signal before and after correction in the luminance component correction step;
The color difference component correction step includes:
An image processing method, wherein the color difference component of the image signal is corrected using the correction amount of the color difference component calculated in the color difference component correction amount calculation step. In any of claims 10 to 12,
A signal extraction step of extracting a signal in a given spatial frequency band from the luminance component of the image signal;
The luminance component correction amount calculating step includes:
A luminance gain calculating step of calculating a luminance gain corresponding to the level of the luminance component of the image signal,
An image processing method for calculating a correction amount of the luminance component based on the signal in the spatial frequency band extracted in the signal extraction step and the luminance gain calculated in the luminance gain calculation step. . An image display method for displaying an image based on an image signal,
A luminance component correction amount calculating step for calculating a correction amount of a luminance component of an image signal only for an image signal in a given luminance level range in a given spatial frequency band;
A luminance component correction step of correcting the luminance component of the image signal using the correction amount calculated in the luminance component correction amount calculation step;
An image display step of displaying an image based on the image signal corrected in the luminance component correction step. An image display method for displaying an image based on an image signal,
The spatial frequency changes in the first direction of the image, the level of the luminance component of the image signal changes in the second direction that intersects the first direction, and the AC component of the luminance component is uniform throughout. An image processing step for correcting the image signal of the image;
An image display step of displaying an image based on the image signal corrected in the image processing step,
The image display step includes
An image display method, comprising: displaying an image having non-uniform luminance AC components in a given luminance level range in a given spatial frequency band.